1. Field of the Invention
The present invention relates to electrophotographic imaging apparatus, and, more particularly, to a latch mechanism securing the fuser unit in the apparatus.
2. Description of the Related Art
In the electrophotographic process commonly used in printers and the like, an electrostatic image is created on photosensitive material such as a belt or a roll. Tiny marking particles, called toner, are applied to the electrostatic image on the photosensitive material. In a monochrome printer, toner is applied in a single station, as only black toner is used. However, in a color printer, separate application stations are provided for black, magenta, yellow and cyan toners. The toner image is then transferred to the desired media, which may include paper, cardstock, envelopes, transparencies or the like. The applied toner image is not, however, permanent until the toner particles are fixed to the receiving media.
To permanently adhere the toner to the media, the media with the toner image thereon is passed through a fuser unit, in which heat and pressure are applied to the toner image. The heat causes constituents of the toner to flow into the pores or interstices between fibers of the media. Pressure in the fuser promotes settling of the toner constituents into these voids. As the sheet exits the fuser, the toner is cooled and solidified, adhering the image to the media.
A commonly used fuser assembly is a roll fuser, which includes two rolls nipped together, with at least one of the rolls being internally heated. The non-heated roll, or back-up roll, is urged against the hot roll, to form a fuser nip through which the media passes.
As a result of the conditions present in the fuser, including high temperature and high pressure, components of the fuser system may have a life span shorter than other machine components, and shorter than the expected life of the base machine. Therefore, it is expected and required that the fuser or various components thereof will be replaced periodically during the useful life span of the machine. To ease replacement of the expired fuser components, various components are unitized, that is the replaceable components are included in a single unitary assembly having a frame and mounting structures compatible with receiving assemblies and structures in the base machine. When replacement is required, locking components are released, the expired fuser unit is removed, a replacement fresh fuser unit is installed and the locking components are re-engaged.
In past fuser designs, it is known for replacement of the fuser to be a service event performed by trained maintenance personnel. However, with more refined unitization of components, and the standardization of life expectancy for various components of the fuser unit, it is desirable that fuser units be designed to be replaced by the customer. Such units are referred to as a CRU or customer replaceable unit. In designing a CRU, it is necessary that the unit be removed and inserted into the base machine easily and accurately, and that it be sufficiently robust to take reasonable amounts of abuse from an untrained installer. Further, it is essential that the CRU be accurately and easily positioned relative to mating components of the base machine when latched into the base machine. Mating drive gears, paper guides and the like must relate accurately and precisely, to minimize misalignment and allow the machine to perform reliably. Even slightly misaligned gears can wear significantly in a short period of time, and fail prematurely. Misaligned paper paths can cause paper jams.
Although computer equipment, such as a printer, is packaged for shipment in a strong shipping container, with packing material limiting movement of the equipment in the container, the containers can be dropped, bumped or jostled during handling and delivery. Even though the printer housing is stabilized within the container, if the container is dropped, a shock can be transmitted to the internal components of the printer. In new office layouts, cubicles, workstations and the like are frequently moved and rearranged. Computer and printing equipment also must be portable and capable of rearrangement and moving. Printers have become smaller, lighter and more easily and conveniently moved. However, equipment may be moved by untrained personnel, even the user, and during a move a printer can be jarred while being transported from one location to another. Therefore, it is essential that a fuser CRU be adequately secured in the housing to withstand a relatively jarring event, such as if the printer is bumped or dropped.
Known latching schemes for fuser CRUs include conventional screws, thumb screws, levers and ninety degree latches. While most of these latching schemes work adequately to retain the fuser in the machine housing, each has drawbacks in design or use. The major drawback of a plain screw latching scheme to retain the fuser in the housing is that the customer is required to use a tool for detaching the expired unit and attaching the replacement unit to the machine. For any customer performed service, it is desirable to eliminate the need for tools, as appropriate tools may not be conveniently available and untrained personnel performing the service may not be comfortable or skilled in using the required tool.
A drawback to the use of plain screws and thumb screws in the latching schemes for fuser CRUs is the possibility of stripping or damaging the threads during use. The untrained user may over-tighten either a conventional screw or a thumb screw, particularly if the user selects a powered driver for operating the screw. Further, screw assemblies often include the use of a metal insert in a plastic part, and insertion of the screw may result in detachment of the metal and plastic components. If threads or inserts are damaged, the fuser will not be located or restrained adequately. Further, if conventional or thumb screws in different parts of the CRU are not similarly tightened, the fuser may skew and bind during insertion or operation. For these and other reasons, neither conventional screws nor thumb screws are desirable latching schemes for fuser CRUs.
Both levers and ninety degree latches are more intuitive and less prone to assembly problems than conventional screws or thumb screws. A drawback to the use of levers and ninety degree latches in latching schemes for fuser CRUs is the size and cost of the lever system or ninety degree latch. To achieve adequate mechanical advantage for levers and latches, to minimize the effort required to perform the latching process, the levers and latches must have a reasonably long length from a pivot or fulcrum point to the force application position. The length or size of the lever or latch systems often take valuable space in the machine, working against the desire to make printers smaller and more compact. Further, if the latch mechanism is to restrain the fuser during a drop event, the strength requirements for the lever or latch mechanism can become relatively expensive. To reduce cost, it is known to use plastic latches in combination with metal tabs on the machine frame to restrain the fuser. However, drawbacks to this solution include the requirement that the customer lift the relatively heavy CRU fuser over the tabs in the machine in order to remove the fuser, and to install the new fuser, which can be awkward and non-intuitive. The user can be confused as to how to properly perform the operation. The need to consult a user manual is undesirable, as the user manual may become separated from the machine, and many users will not willingly take the time to consult written instructions. Further, the tolerances from the formed tab on the machine base to the fusers mating components are substantial, making it difficult to control the fuser final resting position.
Therefore, what is needed is a fuser latch system that is intuitive and easy to operate, both for disengagement and reengagement of fuser CRUs, and which accurately positions the CRU for use while adequately securing the CRU to withstand significant jarring. What is further needed is a fuser latch system which is reliable and inexpensive to manufacture.
The present invention provides a fuser unit latch system suitable for securing a customer replaceable fuser in a base machine, such as a printer.
The invention comprises, in one form thereof, a latch system for a fuser unit in a base machine. The latch system includes a datum receiver provided on the base machine, and a retainer connected to the base machine. The retainer has an enclosed space, with a lateral opening thereto. A frame carries the fuser unit, and has a datum configured to engage said receiver. A shaft is connected to the frame and is rotatable and axially translatable relative to the frame. An end of the shaft is adapted to be received in the enclosed space upon axial translation of the shaft. A handle connected to the shaft is movable between locked and unlocked positions upon rotation of the shaft, and has means for securing the handle in the locked position.
The invention comprises, in another form thereof, a latch system for a fuser unit in a base machine. The latch system includes a frame carrying the fuser unit, the frame having a front side, a rear side and first and second lateral sides. A first retainer is connected to the base machine, near the first lateral side of the frame, the first retainer having a first enclosed space with a lateral opening thereto. A second retainer is connected to the base machine near the second lateral side, the second retainer having a second enclosed space with a lateral opening thereto. The first and second retainers are positioned in the base machine near the rear side. A first shaft is connected to the frame near the first lateral side, and a second shaft connected to the frame near the second lateral side. The first shaft and the second shaft are each rotatable and axially translatable relative to the frame. A first end of the first shaft is adapted to be received in the first enclosed space by axial translation of the first shaft. A second end of the second shaft is adapted to be received in the second enclosed space by axial translation of the second shaft. A first handle connected to the first shaft and is movable between locked and unlocked positions, the first handle having first locking means for securing the first handle in the locked position. A second handle connected to the second shaft and is movable between locked and unlocked positions, the second handle having second locking means for securing the second handle in the locked position.
The invention comprises, in still another form thereof, a latch system for a fuser unit in a base machine, including a frame for the fuser unit. Mounting datums on a front side of the frame are provided for securing the front side of the fuser unit. Datum receivers in the base machine engage the datums and release the datums by movement of the frame. A first latch mechanism and a second latch mechanism are disposed at a rear side of the frame. The first latch mechanism is disposed near a first lateral side of the frame and the second latch mechanism disposed near a second lateral side of the frame. The first latch mechanism has a first eccentric body, and the second latch mechanism has a second eccentric body. A first retainer and a second retainer in the base machine are configured and arranged for receiving the first eccentric body and the second eccentric body, respectively.
The invention comprises, in a further form thereof, a method for securing a fuser in a base machine including steps of providing datums on a forward side of the fuser and datum receivers in the base machine for engaging the datums; sliding the fuser and engaging the datums and receivers; providing a first latch mechanism and a second latch mechanism, each having a fuser component and a base machine component; sliding each of the fuser components axially outwardly; inserting the fuser components into the base machine components; and rotating the fuser components in the base machine components.
The invention comprises, in a still further form thereof, a latch system for securing a first frame in a second frame. The latch system comprises a holder having a datum on one of the frames and a datum receiver on the other of the frames. The datum and the receiver are configured and arranged for the receiver to engage the datum by sliding one toward the other. A latch has a retainer on one of the frames and an axially translatable shaft on the other of the frames. The shaft has a body receivable in the retainer. The holder and the latch are disposed on opposite sides of the frames.
An advantage of the present invention is that the latch system is easy to understand and simple to operate, making the latch system suitable for use in a customer replaceable fuser unit.
Another advantage is that the latch system is compact, requiring minimal space in a printer or the like employing the latch system on a fuser CRU, and the latch system is less expensive to build than more complicated systems, thereby reducing the expense for a CRU.
Yet another advantage is that the latch system holds the fuser unit securely in position, and can withstand some jarring, such as if a printer having a fuser retained by the latch system were bumped or dropped, thereby reducing the potential for hardware damage during such an event.
A further advantage is that the latch system properly aligns the fuser unit in the base machine and properly biases the fuser against a given reference surface, thereby controlling gear mesh and orienting paper paths to reduce the potential for paper jams and premature gear wearing resulting from misaligned machine components.
A still further advantage of the present invention is that operation of the latch system is intuitive, even to unskilled and untrained individuals, and the latch system is reliable.